This invention concerns installations for observation and treatment of the eye by laser radiation and it relates, in particular, to the optical head of such an installation.
A number of eye diseases, like, for example, different types of glaucomas or cataracts, or the disorders resulting from the formation of membranes or filaments of different origins in the eye, can at present be treated by the application of high-density laser radiation in certain regions of the anterior of posterior chamber of the eye.
For that purpose, generally complex ophthalmological treatment installations are used, which combine a stationary laser power generator to produce the laser treatment beam and a moving optical head that can be brought close to the patient's eye and making it possible, notably, to train the treatment beam on the zone to be treated.
An installation of that type is described, for example, in the European patent application published under No. 0 030 210 in the applicant's name. The laser power generator it uses is an Nd-YAG laser that can deliver on Q-Switch mode very short and very high-intensity pulses. The optical head of the installation contains in turn a device for illumination and observation of the zone of the eye to be treated and a marking laser beam generator.
The marking beam is produced, for example, by an He-Ne laser and is formed then by visible radiation. Its function is to materialize the focusing spot of the treatment beam precisely, before release of the pulse, as well as the envelope of that same beam. The latter characteristic enables the operator of the installation to make sure that the treatment beam will not, on passage, reach a zone different from the one to be treated. The marking beam is obtained on exit from the generator by means of a mechanism with rotating prisms that divide the laser radiation produced into two elementary beams, which will turn around the treatment beam so as to materialize its envelope. Detection of the fortuitous encounter of one of those elementary beams with an obstacle is further improved by a modulating device alternately interrupting either beam.
Finally, the optical head of the above-mentioned installation also contains a relatively complex system of optical elements like prisms, mirrors and lenses making it possible to focus the different illuminating, marking and treatment beams on the same spot of the eye, through a contact lens applied to the cornea. In order always to guarantee perfect focusing of those beams on a same spot, on which the observation device must also be focused, while allowing for a displacement of that focusing spot in the axis of the beams, it has proved useful to provide a single focusing lens at the exit of the optical head. Now, the need to bring parallel illuminating and treatment beams as well as the rotating marking beam on that single focusing lens and also to provide means for bringing the focal image into the observation device, has led to a complicated structure requiring numerous successive reflections for the different optical beams.
That is why this invention proposes a simplified optical head no longer necessarily containing an integrated illuminating device. This head embraces a limited number of optical elements, which results not only in a lower cost and a simpler assembly, but also in a better optical efficiency. The latter improvement makes it possible, notably, to reduce significantly the power of the treatment radiation used, and it also results in a greater brightness of the observation device. The advantage thus obtained of increased brightness amply compensates for elimination of the integrated illuminating device, which previously made it possible to focus the illuminating beam on the spot to be treated, avoiding parasitic reflections, but which appreciably complicated the design of the optical head. The new optical head can thus be used without difficulty with any independent illuminating system, of the slit lamp type, which is trained on the patient's eye.
According to one essential aspect of the invention, the optical head is equipped, above the focusing length, with a mirror that simultaneously assures the reflection of treatment and marking beams on that lens and transmission of the observation beam.
The marking and observation beams consisting of visible radiation, in contrast to the treatment beam, that mirror takes advantage of the localization of the marking beam forming the envelope of the treatment beam. For that purpose, it contains a center portion which assures passage of the observation beam and reflection of the treatment beam, and a ring-shaped portion that strikes the marking beam, and which is treated so as also to reflect it.
The invention will be clearly understood by reading the following description, giving in conjunction with the attached drawings, among which: